The present invention is a mobile incinerator system for disposal of low level radioactive solid wastes, both radiological and other conventional aspects having been contemplated. The present invention attempts to reduce low level radioactive solid wastes by means of a process of pyrolytic incineration. U.S. Pat. No. 3,267,890 to Zinn discloses a traditional nonportable fixed incineration system which is not adapted for radioactive wastes. In the Zinn system, the wastes are not hermetically sealed before transferring them into a combustion chamber. Further, the second combustion chamber of the Zinn reference spews out its contents directly to another chamber which is ducted through a gas duct into a cyclone collector. No gas-air heat exchanger is used to reduce the temperature of this waste and to recycle the heat into the original combustion chambers. Zinn uses a double cyclone system to remove particles. This system is not an efficient small particle separator but is entirely appropriate for urban waste disposal since particles of large sizes are generated in the combustion of urban wastes. However, in disposing of radioactive wastes, filters designed to retain particles less than 0.3 micra are needed and this sort of filter is not used in Zinn. Further, in the disposal of nuclear wastes, a wash and chemical neutralization system must be provided for the gases. Zinn discloses no such system but makes use of water merely to reduce temperature of the operating system.
U.S. Pat. No. 4,018,568 to Brewer also discloses a waste disposal system. However, this system is for sewage disposal and not for disposal of radioactive materials. Because of this fact, the Brewer system fails to hermetically seal the waste, and fails to disclose separate venting and neutralizing systems. Brewer instead discloses a catalytic treatment system for gases which is not adequate for radioactive wastes. It is, however, applicable for gases that originate in fermentations, digesters, or incineration at low temperature. Further, the Brewer reference discloses and emphasizes catalytic recombination. This, too, is not necessary in radioactive waste disposal since once carbon dioxide is filtered, it can be emptied into the atmosphere without concern for odor.
The present invention discloses a device specifically for the disposal of radioactive wastes. The invention is mobile and includes a furnace with a rotary combustion chamber having a custom shape that unloads ashes continuously rather than allowing them to sit and compact. Ashes in the present invention pass through the chamber at a constant rate, the rate depending upon the rotary velocity of the chamber. This is an important aspect of the present invention since most prior art devices make use of static burners. Static burners result in the ashes being compacted since they sit in the combustion chambers for long periods of time. The chamber then becomes the holder of hot burning ashes and becomes embedded with calcium and ash. If radioactive wastes were passed through these chambers, the chambers could not later be decontaminated, transported or reused for other uses since the waste would have to some degree embedded itself in the chambers.
A further aspect of the present invention is that the combustion gases pass from the rotary combustion chamber into an expansion chamber and subsequently into a post-combustion chamber where they are oxidized. Thereafter the gases pass into a dilutor and subsequently into a heat exchanger where they are cooled by gas-air tubes refrigerated by venting circuit.
The present invention is mobile and mounted on platforms for easy transportation from location to location.
The present invention can incinerate low level radioactive solid wastes including wood-plastic having a calorific value lower than 4,631 kcal/kg; plastified paper having a calorific value lower than 4,037 kcal/kg; activated carbon with a calorific value lower than 5,500 kcal/kg; textile materials with a calorific value of less than 3,597 kcal/kg; and resins.
Given that the production of incinerable low level wastes increases significantly during plant shutdowns for refueling, optimum use of the present system will be during such outages in order to avoid significant increases of the number of drums containing low level incinerable materials.
The system described herein allows reductions in volume of wastes of a proportion of 1/60 to 1/70.